| 摘要 |
PURPOSE:To improve a cleaning rate by providing a HC shortage judging means, and adjusting a cooled water temperature to a low level when a quantity of an activated seed generated by partial oxidation of HC is judged to be insufficient at the time of reducing NOx, in an internal combustion engine provided with a lean NOx catalyst in its exhaust system. CONSTITUTION:An internal combustion engine 2 is cooled by circulating cooling water between a water jacket formed around a combustion chamber and a radiator 18 through a cooling water circulating passage 20, and a lean NOx catalyst 6 is provided in the exhaust system 4 of the internal combustion engine 2. A bypass passage 22 for bypassing the radiator 18 is provided in the circulating passage 20, and a three way electromagnetic valve 24 is provided in the branching part of the bypass passage 22 from the cooling water circulating passage 20. It is judged by a control device 30 whether the operating condition is such that a quantity of an activated seed generated by partial oxidation of HC is insufficient for the quantity of activated seed required at the time of reducing NOx or not. When it is judged to be in insufficient operating condition, the three way electromagnetic valve 24 is controlled so that a cooling water temperature is adjusted low. |
